The three primary approaches used to clean commercial and residential carpets are steam or hot water, foam and dry systems. Dry-type carpet cleaning systems are further divided into two broad categories. One uses a dry or substantially dry powder and the other uses granules, each of which is several times larger than a powder grain. The granules are slightly moistened with cleaning solvents for dirt removal. The inventive machine has utility for both categories of dry systems but relates primarily to those using granules rather than powder. Such machine also has utility in situations where only carpet vacuuming is performed. That is, its long-bristled brushes are highly effective in removing loose sand and other soil not requiring the application of solvent-bearing material.
Of the dry granular carpet cleaning systems, the best known and most widely used is the HOST.RTM. dry extraction system offered by Racine Industries, Inc. of Racine, Wis. The HOST.RTM. system applies granules to carpet fibers using a machine as shown in Rench et al. U.S. Pat. Nos. 2,842,788 and 2,961,673. Such machine, sold under the HOST.RTM. trademark, is devoid of vacuum capability and has a pair of spaced brushes counter-rotating at relatively low speed (about 350 rpm) to stroke the cleaning granules into, through and across the carpet and its fibers.
The granules are referred to as "dry" and are substantially so even though moistened with cleaning solvents. When stroked as described, these granules "scrub" dirt and soil from such fibers including oily and non-oily soil. The carpet is cleaned by working the HOST@ machine across it in different directions. During the cleaning process, granules migrate to the carpet backing adjacent the base of the fiber. A few granules also adhere lightly to the fibers along their lengths. Heretofore, conventional carpet vacuum machines have been used for removing these dirt-ladened granules.
S. C. Johnson Co. of Racine, Wis., sells a vacuum cleaning machine known as the VECTRON.TM.. Such machine is said to incorporate "dual cyclonic technology" which eliminates the need for a dust bag. The machine can be used for hand vacuuming using a wand. However, one must take the entire machine to the site to do so. The vacuum air stream is not required to flow through collected waste and it is not known whether such machine has a beater bar. An advertising brochure says the machine is "ideal for dry carpet cleaning systems." It is believed that this statement alludes to powder systems since the brochure goes on to say that the machine "does not exhaust powder." It is also believed that such machine is based upon one or both of the following U.S. Pat. Nos. 4,643,748; 4,853,008 (Dyson).
A difficulty attending the use of conventional machines for granule removal is that they perform less than optimally when vacuuming dried-out granules. Performance of such machines is even less satisfactory when vacuuming damp granules and longer carpet fibers further impair granule cleanup. Repeated passes of conventional machines over carpet surfaces are often used and, even at that, such machines fail to remove substantially all of the spent granules.
Whether damp or dry, such granules (at least those of the HOST.RTM. product) do no damage whatever to carpet even though allowed to reside in the carpet for extended periods. But, through carpet usage, granules hidden after vacuuming work their way to the top of the carpet. They are considered by a few to be somewhat unsightly. An approach used by professional cleaners to overcome this is to perform additional vacuuming on one or more successive days--worthwhile even if only to remove newly-deposited dirt--to remove particles which emerge through use.
Yet another difficulty attending the use of conventional machines is that many use only a single filter medium, often a disposable paper bag. To the extent the machine picks up granular material, such bags fill rapidly and work must be suspended during bag disposal and replacement. And many bag/machine configurations draw air through the collected dirt. Vacuum efficiency drops rapidly as the bag fills.
Another disadvantage of conventional machines is that professionals using dry granular carpet cleaning methods are virtually required to invest in two machines, one for brushing the granules into the carpet during non-vacuum cleaning and a vacuum machine for later cleanup. Pairs of machines are cumbersome to move into, around in and out of work sites and represent a significant business investment.
"Dual-mode" (cleaning and vacuum) machines are available for cleaning carpet but they use a dry powder rather than granules. One such machine is made by Clarke-Gravely Corporation of Muskegon, Mich. and sold as the CLARKE CAPTURE carpet cleaning system. Such machine distributes cleaning powder onto the carpet and works the powder into and through the carpet fibers using a round, disk-like scrubber brush, the axis of rotation of which is normal to the carpet surface. Since the machine vacuum system operates to reduce dust rather than recover dirty powder, one is still required to use a separate conventional vacuum machine to remove such powder.
Another type of system used for cleaning carpets with powder is the DRYTECH cleaning machine sold by Sears, Roebuck & Company. The machine has a self-contained vacuum capability and one beater bar with several rows of short-bristled brushes. Such bar is within a shroud which generally conforms to the shape of the bar and by which vacuum is selectively applied. As the brush alone is rotated at high speed, powder is dispensed through two slits, one on either side of the bar between the bar and the shroud. Later, the vacuum is actuated and dry powder (with dirt entrained) is said to be dislodged by the brush and drawn away by vacuum.
A failure of a machine, like the DRYTECH machine, to fully recover powdered cleaner is often not recognized by the site owner/user. This is so since such powdered cleaner is virtually invisible even if distributed on the carpet surface.
Another consideration in machine selection is whether or not the filter media are self-cleaning to any degree. Ways to accomplish forced air cleaning of filter media (although not necessarily in a carpet vacuum machine) are shown in U.S. Pat. Nos. 3,898,065 (Coffman), 2,500,747 (Ellis), 4,826,512 (Fuller), 4,261,713 (Bourdois et al.) and 3,320,726 (Black, Jr.). They describe the use of air jets or air blasts in one way or another to knock dirt off of a filter. There are several variations to this basic approach. One is simply to "pulse" the filter periodically with one or more air jets. In one such arrangement (shown in the Ellis patent), the filter media are rotated so that the air jets sweep across the media surface once for each revolution. Another variation includes backwashing the filter with air; that is, air flows through the filter in a direction opposite normal flow. The Fuller, Bourdois et al. and Black, Jr. patents illustrate this approach.
U.S. Pat. Nos. 3,785,123 (Leith) and 3,685,257 (Burke) describe filter cleaning using air in other ways. The Burke patent describes cleaning of the inner or outer surfaces of cylindrical filter bags using traveling vortex gas rings. Such rings appear to be donut shaped regions of high velocity air movement. The cleaning method shown in the Leith patent uses traveling turbulent air flow to "ripple" filter bags and clean particulates from the bag inner surface. The traveling turbulent air flow results from counter-rotation of inner and outer concentric cylinders.
vacuum cleaning machines using cyclone separators are shown in representative U.S. Pat. Nos. 4,826,515 (Dyson) and 3,877,902 (Eriksson et al.). Amway Corporation has a Carpet Maintenance System CMS 1000 machine which uses a conventional "beater bar" brush with spirally-arranged brush tufts. Air flow is understood to be first through a cylindrical collection chamber at high velocity, then through a cyclone separator at higher velocity and then through a "HEPA" filter located below a cylindrical collection chamber. The machine is said to have "parallel dual centrifugal separation chambers." It also has a transparent removable waste collection compartment.